A vehicle such as an automobile is provided with a power steering device which uses oil pressure. Conventionally, to supply this oil pressure, a vane pump is used such as is shown in FIG. 13 and FIG. 14.
The vane pump houses a cam ring 30, a rotor 31 and vanes 32 which form a pump cartridge 3 in the inner circumference of a body 107. The cam ring 30 and rotor 31 are disposed between a cover 106 tightened to the body 107 and a side plate 108 fixed to the inner circumference of the body 107.
The rotor 31 is joined to a drive shaft 50' which passes through the body 107. A pulley is joined to a base end 50'B of the drive shaft 50', and the pulley is connected with an engine. The drive shaft 50' drives the rotor 31 and vanes 32. The drive shaft 50' is supported by a bearing 120 provided in the body 107 and a bearing 121 provided in the cover 106. A tip end 50'A on the bearing 121 side of the drive shaft 50' is housed inside the cover 106 without penetrating the cover 106.
A ring groove 52 is formed at a predetermined position on the outer circumference of the drive shaft 50', and a cir clip 33 engages with the ring groove 52. The relative displacement of the rotor 31 and drive shaft 50' in the axial direction is thereby regulated, and the rotor 31 is joined to the drive shaft 50'.
When a force acts on the drive shaft 50' in such a direction as to push it away from the body 107, the cir clip 33 comes in contact with the rotor 31 which slides on the side plate 108, and the displacement of the drive shaft 50' in the axial direction is thereby regulated.
A high pressure chamber 101 formed between the inner circumference of the body 107 and the side plate 108, a passage 111 connecting the high pressure chamber 101 and a flowrate control valve 4, an intake connector 105 connecting with the outside of the body 107, and a low pressure passage 109 for recirculating excess hydraulic fluid in the flowrate control valve 4 to the pump cartridge 3, are provided inside the body 107.
Hydraulic fluid is supplied under pressure from the pump cartridge 3 via a connecting hole in the side plate 108, and the required amount of hydraulic fluid is supplied to the power steering device via the passage 111 and flowrate control valve 4.
Surplus flowrate from the flowrate control valve 4 and hydraulic fluid from the intake connector 105 flow into the cover 106 via the low pressure passage 109. The hydraulic fluid is sent to an intake area of the pump cartridge 3 via branch passages 102, 102 formed in the cover 106. As the cover 106 comprises the branch passages 102, 102, it is formed by demolding using a core. A thick part 106A of predetermined thickness is formed between the branch passages 102 and a contact surface of the cover 106 with the rotor 31 and vanes 32, and strength is thereby ensured.
Hydraulic fluid which has leaked from the end face of the cam ring 30, and from a gap between the rotor 31 and the side plate 108 flows back to the low pressure passage 109 from the outer circumference of the bearing 120 via a drain passage 112 inclined at a predetermined angle to the drive shaft 50'.
However, in the aforesaid prior art, the drive shaft 50' is supported by the bearing 120 in the body 107 and the bearing 121 in the cover 106. Therefore, when the vane pump is assembled, an assembly step must be provided to press the bearing 121 into the cover 106. The contact surfaces between the cover 106 and the body 107 also must be finished with a predetermined surface precision in order to ensure orthogonality of the cover 106 and drive shaft 50' and concentricity of the bearing 121 and drive shaft 50'. Therefore, the number of machining steps increases, machining time increases, and production costs rise.
The displacement of the drive shaft 50' to the right-hand side of FIG. 13 is restricted by the cir clip 33, and when it displaces to the left-hand side, the end 50'A of the drive shaft 50' comes in contact with the inner circumference of the cover 106. Therefore, the depth of the hole into which the bearing 121 is inserted requires to be strictly controlled. As machining is necessary after casting the cover 106, the number of machining steps and machining time increase, and production costs increase.
As shown in FIG. 14, the positional relationship of the cam ring 30 and side plate 108 is determined by a pair of dowel pins 42, 42 which pass through the cam ring 30 and side plate 108. The dowel pins 42are pressed into positioning holes, not illustrated, formed on the surface of the cover 106 on which the rotor 31 and vanes 32 slide. Therefore, the number of machining steps and machining time increase in order to ensure machining precision of this hole.
The vane pump having the aforesaid construction is assembled by assembling each component sequentially to the body 107 or cover 106, so the number of assembly steps increases. Further, automation of assembly steps is difficult, and productivity cannot be improved.
This invention, which was conceived in view of the aforesaid problems, largely reduces the number of steps used in assembling the vane pump by reducing the steps for machining the cover, and thereby improves productivity. It is a further object of the invention to provide a vane pump whereof the assembly can be automated.